Chemoproteomic Identification of AKT2 as a Paclitaxel‐Binding Protein via C─C Bond‐Linked Probe PTX‐4 in Paclitaxel‐Resistant Breast Cancer

Breast cancer remains one of the most prevalent malignancies among women, and taxane-based chemotherapies such as paclitaxel and docetaxel are central to standard treatment regimens. However, drug resistance in breast cancer limits therapeutic efficacy and contributes to recurrence and metastasis. Identifying resistance-associated molecular targets is therefore critical for advancing treatment strategies. To investigate paclitaxel resistance, we designed and synthesized four paclitaxel-derived probes. Among these, PTX-4, constructed via a stable C─C bond linkage, exhibited superior efficiency. Using a chemoproteomic approach, we systematically profiled paclitaxel-binding proteins in parental and resistant breast cancer cells. This strategy successfully identified AKT2, an unrecognized paclitaxel-interacting protein in paclitaxel-resistant breast cancer. Functional validation demonstrated that AKT2 is a direct target of paclitaxel in paclitaxel-resistant cells. Knockdown and pharmacological inhibition of AKT2 restored the sensitivity of paclitaxel-resistant cells to paclitaxel. These findings establish AKT2 as a key mediator of paclitaxel resistance in breast cancer. Targeting AKT2 may offer a promising therapeutic strategy to overcome resistance and improve the clinical efficacy of taxane-based chemotherapy. This study highlights the advantage of C─C bond-linked, pharmacologically active probes for chemoproteomic profiling of drug targets.